olar thermal tie-in hot water to air heat exchangers

Mark Custis

start with the coil manufacturer's engineering tables. From there one could interpolate yields.

michael_34

solar thermal tie-in hot water to air heat exchangers

Hi All,
Has anybody tried to tie in solar thermal to forced air furnace with a hot water to air heat exchanger. Almost any info helpful. : )
Michael

Paul Pollets

Sizing

You would need a very large array to provide the amount of BTu's necessary. Depending upon where you live.... N. of the Mason-Dixon, extremely impracticle and costly. When the demand for heat is the highest, (Dec-Jan) the sun angle is the lowest.

The best bang for the buck is a solar DHW system.

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michael_34

Paul,
Thanks for your response. Believe me I understand all that. What I am looking for is facts.
I want to know the efficiency of these hot water to air heat exchangers. I want to see numbers.
Thanks
Michael

hot_rod

coil area

usually gets larger with solar supplied coils, based on supply temperature of course.

A coil manufacturer would be the best place to start. Supply them with loads, supply temperatures, air handler info, etc.

Myson built Solar-Vectors years ago for direct tie in to solar arrays. These were small wall mounted convectors, generally one per room. I still know of some in my area, 20 plus years of service!

It's certainly possible to drive air coils with solar, even flat panels, you just need to do the math.

Of course a back up heat source will be needed. Adding a HW coil to a furnace or AH is a good way to go, if it can be sized correctly.

This is also how most of the OWF (outdoor wood furnaces) are used for heating, via HW coils on the forced air system.

hr

michael_34

Hot Rod,
I emailed several manufactures of these type of heat exchangers and no feed back as of yet. I know that OWF are using them and I have not found anyone who has done it with Solar. I would like to see some of the numbers that were ran on a solar tie in system before and after.
This customer has the means of doing this and is very Gung Ho. I want a system that works properly. He has 2100 sq ft to heat and is planning two separate additions to his home with radiant floors. I want to gather as much knowledge as I can on this. Then get my ducks and a row and decide how I want to proceed from there. Thank you for input as always and anything else you got throw it at me.
Thanks again
Michael

hot_rod

software to help

Here is one companies design software

www.firstco.com/software/coil_calculation.asp

But if you don't know all the science, terms, and engineering behind air flow, it may be better to call one of the reps for air coils. They can size a coil in a metter of minutes if you give them all the data.

There is an old boy locally that still sizes with hand formuas! But he knows the how and whys better than the software users in many cases.

Keep trying the dealers or reps in your area. There are coil specfic reps or the usual HVAC reps know this stuff. Carrier, Lennox, Trane, York, Whirlpool are a few of the big names.

First Company, McQuay, Airtherm there are dozens of coil only manufacturers.

Try Eugene down below this list. he certainly knows air handling

hr

Mike C._4

solar to air HX exchanger

I use a modine hot water heater for the dump or secondary side of my solar system after the DHW is heated. It just blows the warm air to my open basement. This is until pool season opens and I will dump to that. Though it does work well for heating, typically it is only working later in the day when it is sunny and you don't necessarily need the heat. That's the problem. You can size the array and HX as big as you want but without storage it won't be useful. If storage is used then it going to be gigantic to be able to store any useable amount of heat at the higher temps required. The temperature needed for an air exchanger is going to be typically much higher than say a low temp radiant floor system. I would say get the DHW going with maybe some expectation of getting solar hooked up to any future radiant floor system with storage. I think your customer's expectation of having an air HX work "properly" needs a reality check. Unless of course he really has the means to throw a lot of money at it. I can't imagine any HX company is going quote numbers based on solar useage. Just too many variables. They'll give you the outputs at certain temps supplied but you'll have to do the educated guesswork for the solar side. If I were to do a hot air system I would just use hot air solar collectors and heat directly.

Mike